Bacterial plaque is a thin, colourless and sticky, almost invisible film that is being formed continually on the teeth, in the greater part, but also on the back of the tongue, palate, mucous membrane, vestibule and lips. It is composed of bacteria, saliva and remains of foodstuffs and it is the main cause of the 2 most common dental diseases: tooth decay and periodontal disease. Daily dental hygiene is essential for removing plaque and keeping the mouth healthy.
Tooth decay is a localised infectious process, of external origin, that causes the debilitation of the hard tissue (enamel) of the tooth and leads to the formation of a cavity. The main etiologic agent causing this dental disease seems to be the gram (+) bacteria Streptococcus mutans. 
Periodontal disease is a disease that affects the gums and the structures supporting the teeth. The earliest stage in periodontal disease is gingivitis and it is characterized by a reddening of the gums that become inflamed and bleed easily. If the disease is not appropriately treated at that stage it can develop into periodontitis and cause irreversible damage to the gums. In periodontitis, the most advanced stage in periodontal disease, the bone and the tissue that surround the teeth are destroyed and pockets are formed in the gums that are filled with more bacterial plaque. As the disease progresses, the teeth become slack or loose and can eventually fall out or require extraction.
The main cause of periodontal disease is the bacterial plaque which, if it is not removed, hardens and builds up on the teeth. The toxins produced by the bacteria present in the bacterial plaque destroy supporting tissue around the teeth, the gums loosen and the teeth separate forming the pockets that are filled with bacterial plaque.
Periodontal disease can be prevented by removing the bacterial plaque by means of frequent and careful brushing and with the help of dental floss and, optionally, with the use of interdental or interproximal brushes, interdental stimulants and/or mouthwashes. However, daily cleaning is not sufficient and it should be completed with professional cleaning carried out by a dentist that will remove the hardened deposits that have been formed and could not be removed by daily brushing.
The usual treatment of periodontal disease consists of scraping, curettage and radicular planing, which implies removing the plaque and the calculus from the pockets around the teeth, polishing and planing the roots with the aim that the gum adheres again to the tooth or contracts enough to eliminate the pocket. However, the most advanced cases can require surgical treatment.
On the other hand, halitosis or bad breath, is a dysfunction caused by the production and liberation of diverse volatile compounds, mainly volatile sulphurated compounds (VSC), such as hydrogen sulphide and methyl mercaptan. The buccal cavity contains microorganisms, in general, anaerobic bacteria and gram (−) bacteria, responsible to a certain extent for the occurrence of halitosis. Diverse treatments exist to combat halitosis, some based on the administration of synthetic products while others are based on the administration of natural products [see Spanish patent application No. P9701545].
In spite of having diverse means to prevent and to treat bacterial plaque, and to treat halitosis, there continues to be a need to increase the arsenal of remedies for combating the formation of bacterial plaque and/or the presence of noxious microorganisms in the buccal cavity.
The present invention provides a solution for said existing necessity that consists in employing olive oil in the preparation of an oral hygiene product intended for eliminating or reducing the bacterial plaque and/or noxious bacteria present in the buccal cavity. As a consequence of this total or partial reduction of bacterial plaque and/or of the bacteria present in the buccal cavity, the occurrence is decreased of oral diseases, decay, periodontitis and its first stages (gingivitis), as well as halitosis associated with the production of VSC by microorganisms present in the buccal cavity.
Olive oil is a product habitually used in food although other therapeutic and cosmetic applications are also known [see Spanish patent application No. 9801543]. Oleic acid [cis-9-octadecenoic acid] is a monounsaturated fatty acid that seems to be the responsible for numerous beneficial effects of olive oil. It is very well known that oleic acid helps in the prevention of arteriosclerosis, increases the level of cholesterol connected with high density lipoproteins and reduces the level of cholesterol connected with low density lipoproteins, achieving in this way an appropriate manner of combating the occurrence of cardiovascular diseases.
Olive oil contains, also, vitamins (A, E, F and K) and polyphenols and it seems to be that the antioxidant substances present in olive oil (vitamins A and E and polyphenols) provide the organism with a defence mechanism that delays aging, prevents arteriosclerosis, the appearance of breast cancer, hepatic disorders and inflammation.
Olive oil is well tolerated by the stomach, has beneficial effects on gastritis and ulcers, is a cholagogue, activates the secretion of pancreatic hormones and bile, and diminishes the incidence of cholelythiasis. On the other hand, its excellent digestibility results in the complete absorption of nutritients, especially vitamins and mineral salts and it contributes the necessary oleates for the bone system. The mineralising effect that is exercised by olive oil is excellent both in childhood and when aging, a stage in which mineralisation problems usually appear.
Olive oil also has a beneficial effect on the brain and on the central nervous system, it protects the body against the occurrence of infections and assists in the healing of internal and external tissue.
Besides the aforementioned therapeutic indications, olive oil has cosmetic applications and at the moment it is beginning to be used as a skin protector, acting against the appearance of wrinkles and as a lotion for dry and scaly skins. It is also used to restore shine and vigour to damaged hair and eyelashes and to recover the vitality of fragile hair.
In the Mediterranean region olive oil is known for its capacity as a preservative and germicide (it is used to preserve fish, vegetables, cheese, etc.). In the case of such products as cheese or fish that can contain a great quantity of bacteria when initially immersed in olive oil, the bacteria count obtained is practically nil after a few hours from their immersion in olive oil.
It has been found that, surprisingly, olive oil can be used to reduce or to eliminate bacterial plaque and/or the bacteria present in the buccal cavity.